BUTTE COUNTY, CA (MPG) - As West Nile Virus (WNV) season approaches, Butte County Public Health (BCPH) urges horse owners to vaccinate horses for WNV, a mosquito borne illness transmitted to animals and people through the bite of an infected mosquito. In 2021, 13 California horses were confirmed positive for West Nile Virus. Of these horses, two died or were euthanized due to the severity of their illness.

The most effective way to prevent WNV in horses is by vaccination. Annual WNV vaccination is recommended for horses, ideally, prior to mosquito season. WNV season runs June through October in Butte County.  Several vaccines are available for horses. Check with your local veterinarian to discuss the best option for your horse. 

Horses are at higher risk for WNV because they spend most of their time outdoors, including dusk and dawn, when mosquitos capable of transmitting WNV are most active. WNV carrying mosquitoes breed in standing water, including ponds, water troughs and irrigation run-off, increasing the risk of WNV for horses and humans.

“Vaccination is a safe, inexpensive, and very effective way to prevent WNV, a disease that results in death or euthanasia in one-third of affected horses,” stated Dr. Linda Lewis, Veterinarian and Epidemiologist at Butte County Public Health.

WNV may cause a wide range of symptoms for horses, including those that mimic other serious neurological illness such as rabies and equine herpes virus, toxins, and other conditions causing brain dysfunction. Consult a veterinarian if your horse exhibits any of the following symptoms:Stumbling or lack of coordination; Drooping lips, lip smacking or teeth grinding; General weakness, muscle twitching and/or tremors; Sensitivity to touch or sound; Fever; Difficulty rising or inability to rise; Convulsions or coma.

In addition to vaccination, horse owners can take steps to prevent WNV in their horses by reducing mosquitoes on their property, including draining standing water, scheduling pasture irrigation, cleaning containers that hold water every week and stocking water tanks and ponds with mosquito fish. Reduce exposing horses to mosquitoes by applying mosquito repellent during dusk and dawn and by circulating air in barns by using fans.

For more information about West Nile Virus, visit:

Butte County Public Health, WNV page: www.buttewnv.com

Butte County Mosquito & Vector Control District: www.buttemosquito.com